The invention relates to retainers that encircle the bundles of cords or similar structures and hold them together.
Cable ties have long been used to bundle elongated articles together. Waxed string was one of the earliest devices used to simply tie electrical wire together. Eventually the string was replaced by the plastic cable tie that is made of a highly resilient thermoplastic material. In general, most commercially available cable ties consist of an elongated flexible strap having a pointed or rounded tip at one end and a locking head at the opposite end. The locking head receives the opposing end and a portion of the strap to form a noose or loop of variable size to retain cables therein. Typically, teeth extend from at least one longitudinal surface of the strap. The locking head has a pawl designed to engage the teeth and retain the strap after the strap is wound around the cables. When inserted into the locking head, the strap is tightened to the desired degree of tension by pulling the strap through the pawl. When tight the end of the strap is released causing the locking head to engage one or more of the teeth preventing the strap from being released.
There are many variations on the strap design. One common tie has a flat rectangular head at one end of a strap. The head has a rectangular slot of a selected length and a smaller selected width. The strap has pairs of wing-like projections that extend from the strap at spaced-apart intervals. The widest portion each pair of the wings is slightly less than the length of the slot in the head. The width of the strap between the wings is slightly less than the width of the slot in the head. The end of the strap opposite the head is fitted through the slot forming a loop by twisting the strap so that the wings extend along the length of the slot. After one or more wings are pulled through the slot, the strap is untwisted so that the wings align with the width of the slot. Typically, the wings are thin enough to bend or flex so that the strap can be pulled through the slot to tighten the loop. The shape of the wings and their rigidity enables the wings to resist forces applied in a longitudinal direction preventing the strap from being backed out of the slot. This type of tie is also made of a highly resilient thermoplastic material.
Another type of tie has a strap having a series of spaced apart projections along its length. These projections may be rectangular, cylindrical or even hemispherical. A head is provided at one end of the strap that has a slot or hook shaped to engage the projections. Examples of this type of strap are disclosed in U.S. Pat. No. 2,900,696 to Bacon, U.S. Pat. No. 2,959,098 to Hassman, U.S. Pat. No. 4,235,404 to Kraus and U.S. Pat. No. 5,402,971 to Bower, as well as in French patents 1.110.010, 1.126.130 and 1.253.973. Most of these patents simply say that the strap can be made of plastic without specifying a type of plastic. Kraus says that prior art cable ties have been made of a highly resilient thermoplastic material such as nylon or HALAR. The tie disclosed in his patent is preferably made of a flexible, tough, slightly rubbery material such as SANTOPRENE 101-87 thermoplastic rubber made by Monsanto Corporation.
While nearly all of the ties disclosed in the prior art have been effective for their intended purpose, they tend to feel hard to the touch. The thermoplastic materials from which they are made have a stiff durometer of above 100. Consequently, these ties can be difficult to work with, especially in cold weather. They can easily scratch or cut bare hands, particularly hands that are chapped and cold. Consequently, there is a need for a tie made from a soft plastic having a durometer in the range of from 60 to 95. Such a tie would be particularly useful for hanging Christmas decorations outdoors since these decorations are often hung and taken down in cold weather. Because such decorations are seasonal the tie should be releasable and reusable. The tie should also be secure enough to withstand winter winds acting on the decorations that they are securing. However, we have found that when prior art cable ties are made of soft vinyl the strap and teeth or projections on the strap flex and stretch so much that the strap can be easily pulled away from the head. For this reason there is a need for a tie made of soft plastic that has a head and strap configuration such that the strap cannot easily be pulled through the head releasing the tie.
We provide a flexible plastic tie having an elongated spine of a selected width. A plurality of hemispherical or rod-like projections are attached to the spine. The projections are arranged in spaced apart pairs such that each pair of projections is co-linear and there is a selected distance between the distal ends of each pair of projections. The selected distance should be substantially the same for all pairs of projections. A fastening head is attached to one end of the spine. The fastening head has a top surface, a bottom surface and outside surfaces extending from the top surface to the bottom surface. There is a generally rectangular slot passing through the fastening head. The slot has a width equal to or greater than the width of the spine and less than the selected distance between the distal ends of each pair of projections, such that the slot and the outside surface define a wall encircling the slot. The elongated spine, rod-like projections and fastening head are integrally molded from a plastic having a durometer of from 60 to 95. Preferably the plastic is polyvinyl chloride, polyethylene or polyurethane. The projections may have a circular, oval, square, rectangular or triangular cross-section. We prefer to provide a seat in the top surface of the head to receive one pair of projections.